In electrical appliances having a cover over a display apparatus, for example with light sources such as LEDs, the color of a visible display depends significantly on the color or the transmission of the cover. On account of this, the color of a display can be colored or else a desired color may be achieved only to a limited extent, depending on the transmission profile of the cover and the color of the light source.
By way of example, hobs as an electrical appliance with a hob plate which is composed of glass ceramic as a cover have a transmission profile for light which is inhomogeneous and has a high transmission in the region of wavelengths of greater than 700 nm. The transmission in the region of wavelengths of less than 700 nm is very low and sometimes lies below 1% or even is 0%. The reason for this can be found in the material properties of glass ceramic which are optimized for suitable use in electric hobs with requirements for stability on the one hand and for transmission in the wavelength region of radiant heating bodies which is as high as possible on the other hand, and even produce the abovementioned low transmission at low wavelengths. Therefore, colors with a low wavelength, that is to say in the yellow, green and blue regions, cannot be displayed or can be only marginally displayed with a display apparatus of the customary design in the case of a described cover.
WO 2012/076412 A1 discloses a display apparatus in which a relatively large color bandwidth can be created for a display, in particular also for a white display, with three primary-color LED lamps by appropriate mixing. However, firstly, this is considered to be relatively costly. Secondly, a combination of three interacting light-emitting diodes cannot be provided for every display that can be used in practice. By way of example, this is not practical in so-called seven-segment displays with an overall height of usually less than 2 cm.